Lemon Polenta Cake - The Local Palate

Ingredients

• 1 cup buttermilk
• ½ cup finely ground polenta or cornmeal
• 1 cup unsalted butter, room temperature
• 1¼ cups sugar
• 4 large eggs
• 1 tablespoon grated lemon zest
• 1 vanilla bean
• 2¼ cups unbleached all-purpose flour
• 2 teaspoons baking powder
• ¾ teaspoon baking soda
• ¼ teaspoon salt
• Lemon Caramel Sauce (recipe follows)
• 2 cups sugar
• 4 tablespoons butter
• 6 tablespoons water
• 12 tablespoons freshly squeezed lemon juice, plus zest
• 1 vanilla bean, split